1 ;;; 8sync --- Asynchronous programming for Guile
2 ;;; Copyright (C) 2015 Christopher Allan Webber <cwebber@dustycloud.org>
4 ;;; This file is part of 8sync.
6 ;;; 8sync is free software: you can redistribute it and/or modify it
7 ;;; under the terms of the GNU Lesser General Public License as
8 ;;; published by the Free Software Foundation, either version 3 of the
9 ;;; License, or (at your option) any later version.
11 ;;; 8sync is distributed in the hope that it will be useful,
12 ;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
13 ;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 ;;; GNU Lesser General Public License for more details.
16 ;;; You should have received a copy of the GNU Lesser General Public
17 ;;; License along with 8sync. If not, see <http://www.gnu.org/licenses/>.
19 (define-module (8sync agenda)
20 #:use-module (srfi srfi-1)
21 #:use-module (srfi srfi-9)
22 #:use-module (srfi srfi-9 gnu)
23 #:use-module (ice-9 q)
24 #:use-module (ice-9 match)
25 #:use-module (ice-9 receive)
28 agenda-queue agenda-prompt-tag
29 agenda-read-port-map agenda-write-port-map agenda-except-port-map
37 make-time-segment time-segment?
38 time-segment-time time-segment-queue
40 time< time= time<= time-delta+
44 make-time-delta tdelta time-delta?
45 time-delta-sec time-delta-usec
48 make-schedule schedule?
49 schedule-add! schedule-empty?
53 schedule-segments-split schedule-extract-until!
54 add-segments-contents-to-queue!
57 make-run-request run-request?
58 run-request-proc run-request-when
61 make-port-request port-request port-request?
63 port-request-read port-request-write port-request-except
66 make-port-remove-request port-remove-request port-remove-request?
67 port-remove-request-port
69 run-it wrap wrap-apply run run-at run-delay
72 8sync-run 8sync-run-at 8sync-run-delay
73 8sync-port 8sync-port-remove
77 ;; used for introspecting the error, but a method for making
80 wrapped-exception-key wrapped-exception-args
81 wrapped-exception-stacks
83 print-error-and-continue
88 start-agenda agenda-run-once))
90 ;; @@: Using immutable agendas here, so wouldn't it make sense to
91 ;; replace this queue stuff with using pfds based immutable queues?
97 ;;; The agenda consists of:
98 ;;; - a queue of immediate items to handle
99 ;;; - sheduled future events to be added to a future queue
100 ;;; - a tag by which running processes can escape for some asynchronous
101 ;;; operation (from which they can be returned later)
102 ;;; - a mapping of ports to various handler procedures
104 ;;; The goal, eventually, is for this all to be immutable and functional.
105 ;;; However, we aren't there yet. Some tricky things:
106 ;;; - The schedule needs to be immutable, yet reasonably efficient.
107 ;;; - Need to use immutable queues (ijp's pfds library?)
108 ;;; - Modeling reading from ports as something repeatable,
109 ;;; and with reasonable separation from functional components?
111 (define-immutable-record-type <agenda>
112 (make-agenda-intern queue prompt-tag
113 read-port-map write-port-map except-port-map
114 schedule time catch-handler pre-unwind-handler)
117 (prompt-tag agenda-prompt-tag)
118 (read-port-map agenda-read-port-map)
119 (write-port-map agenda-write-port-map)
120 (except-port-map agenda-except-port-map)
121 (schedule agenda-schedule)
123 (catch-handler agenda-catch-handler)
124 (pre-unwind-handler agenda-pre-unwind-handler))
126 (define (make-async-prompt-tag)
127 "Make an async prompt tag for an agenda.
129 Generally done automatically for the user through (make-agenda)."
130 (make-prompt-tag "prompt"))
132 (define* (make-agenda #:key
134 (prompt (make-prompt-tag))
135 (read-port-map (make-hash-table))
136 (write-port-map (make-hash-table))
137 (except-port-map (make-hash-table))
138 (schedule (make-schedule))
139 (time (gettimeofday))
141 (pre-unwind-handler print-error-and-continue))
142 ;; TODO: document arguments
143 "Make a fresh agenda."
144 (make-agenda-intern queue prompt
145 read-port-map write-port-map except-port-map
147 catch-handler pre-unwind-handler))
149 (define (current-agenda-prompt)
150 "Get the prompt for the current agenda; signal an error if there isn't one."
151 (let ((current-agenda (%current-agenda)))
152 (if (not current-agenda)
155 "Can't get current agenda prompt if there's no current agenda!")
156 (agenda-prompt-tag current-agenda))))
158 ;; helper for making queues for an agenda
159 (define (list->q lst)
160 "Makes a queue composed of LST items"
168 (define (make-q* . args)
169 "Makes a queue and populates it with this invocation's ARGS"
176 ;;; This is where we handle timed events for the future
178 ;; This section totally borrows from the ideas in SICP
181 ;; NOTE: time is a cons of (seconds . microseconds)
183 (define-record-type <time-segment>
184 (make-time-segment-intern time queue)
186 (time time-segment-time)
187 (queue time-segment-queue))
189 ;; @@: This seems to be the same as srfi-18's seconds->time procedure?
190 ;; Maybe double check and switch to that? (Thanks amz3!)
192 (define (time-from-float-or-fraction time)
193 "Produce a (sec . usec) pair from TIME, a float or fraction"
194 (let* ((mixed-whole (floor time))
195 (mixed-rest (- time mixed-whole)) ; float or fraction component
197 (usec (floor (* 1000000 mixed-rest))))
198 (cons (inexact->exact sec) (inexact->exact usec))))
200 (define (time-segment-right-format time)
201 "Ensure TIME is in the right format.
203 The right format means (second . microsecond).
204 If an integer, will convert appropriately."
205 ;; TODO: add floating point / rational number support.
207 ;; time is already a cons of second and microsecnd
208 (((? integer? s) . (? integer? u)) time)
209 ;; time was just an integer (just the second)
210 ((? integer? _) (cons time 0))
211 ((or (? rational? _) (? inexact? _))
212 (time-from-float-or-fraction time))
213 (_ (throw 'invalid-time "Invalid time" time))))
215 (define* (make-time-segment time #:optional (queue (make-q)))
216 "Make a time segment of TIME and QUEUE
218 No automatic conversion is done, so you might have to
219 run (time-segment-right-format) first."
220 (make-time-segment-intern time queue))
222 (define (time< time1 time2)
223 "Check if TIME1 is less than TIME2"
224 (cond ((< (car time1)
234 (define (time= time1 time2)
235 "Check whether TIME1 and TIME2 are equivalent"
236 (and (= (car time1) (car time2))
237 (= (cdr time1) (cdr time2))))
239 (define (time<= time1 time2)
240 "Check if TIME1 is less than or equal to TIME2"
241 (or (time< time1 time2)
242 (time= time1 time2)))
245 (define-record-type <time-delta>
246 (make-time-delta-intern sec usec)
249 (usec time-delta-usec))
251 (define* (make-time-delta time)
252 "Make a <time-delta> of SEC seconds and USEC microseconds.
254 This is used primarily so the agenda can recognize RUN-REQUEST objects
255 which are meant to delay computation"
256 (match (time-segment-right-format time)
258 (make-time-delta-intern sec usec))))
260 (define tdelta make-time-delta)
262 (define (time-carry-correct time)
263 "Corrects/handles time microsecond carry.
264 Will produce (0 . 0) instead of a negative number, if needed."
265 (cond ((>= (cdr time) 1000000)
268 (- (cdr time) 1000000)))
274 (+ (cdr time) 1000000))))
277 (define (time-delta+ time time-delta)
278 "Increment a TIME by the value of TIME-DELTA"
280 (cons (+ (car time) (time-delta-sec time-delta))
281 (+ (cdr time) (time-delta-usec time-delta)))))
283 (define (time-minus time1 time2)
284 "Subtract TIME2 from TIME1"
286 (cons (- (car time1) (car time2))
287 (- (cdr time1) (cdr time2)))))
289 (define (time-plus time1 time2)
290 "Add TIME1 and TIME2"
292 (cons (+ (car time1) (car time2))
293 (+ (cdr time1) (cdr time2)))))
296 (define-record-type <schedule>
297 (make-schedule-intern segments)
299 (segments schedule-segments set-schedule-segments!))
301 (define* (make-schedule #:optional segments)
302 "Make a schedule, optionally pre-composed of SEGMENTS"
303 (make-schedule-intern (or segments '())))
305 (define (schedule-soonest-time schedule)
306 "Return a cons of (sec . usec) for next time segement, or #f if none"
307 (let ((segments (schedule-segments schedule)))
308 (if (eq? segments '())
310 (time-segment-time (car segments)))))
312 ;; TODO: This code is reasonably easy to read but it
313 ;; mutates AND is worst case of O(n) in both space and time :(
314 ;; but at least it'll be reasonably easy to refactor to
315 ;; a more functional setup?
316 (define (schedule-add! schedule time proc)
317 "Mutate SCHEDULE, adding PROC at an appropriate time segment for TIME"
318 (let ((time (time-segment-right-format time)))
319 (define (new-time-segment)
321 (make-time-segment time)))
322 (enq! (time-segment-queue new-segment) proc)
324 (define (loop segments)
325 (define (segment-equals-time? segment)
326 (time= time (time-segment-time segment)))
328 (define (segment-more-than-time? segment)
329 (time< time (time-segment-time segment)))
331 ;; We could switch this out to be more mutate'y
332 ;; and avoid the O(n) of space... is that over-optimizing?
334 ;; If we're at the end of the list, time to make a new
336 ('() (cons (new-time-segment) '()))
337 ;; If the segment's time is exactly our time, good news
338 ;; everyone! Let's append our stuff to its queue
339 (((? segment-equals-time? first) rest ...)
340 (enq! (time-segment-queue first) proc)
342 ;; If the first segment is more than our time,
343 ;; ours belongs before this one, so add it and
344 ;; start consing our way back
345 (((? segment-more-than-time? first) rest ...)
346 (cons (new-time-segment) segments))
347 ;; Otherwise, build up recursive result
349 (cons first (loop rest)))))
350 (set-schedule-segments!
352 (loop (schedule-segments schedule)))))
354 (define (schedule-empty? schedule)
355 "Check if the SCHEDULE is currently empty"
356 (eq? (schedule-segments schedule) '()))
358 (define (schedule-segments-split schedule time)
359 "Does a multiple value return of time segments before/at and after TIME"
360 (let ((time (time-segment-right-format time)))
361 (define (segment-is-now? segment)
362 (time= (time-segment-time segment) time))
363 (define (segment-is-before-now? segment)
364 (time< (time-segment-time segment) time))
366 (let loop ((segments-before '())
367 (segments-left (schedule-segments schedule)))
369 ;; end of the line, return
371 (values (reverse segments-before) '()))
373 ;; It's right now, so time to stop, but include this one in before
374 ;; but otherwise return
375 (((? segment-is-now? first) rest ...)
376 (values (reverse (cons first segments-before)) rest))
378 ;; This is prior or at now, so add it and keep going
379 (((? segment-is-before-now? first) rest ...)
380 (loop (cons first segments-before) rest))
382 ;; Otherwise it's past now, just return what we have
384 (values segments-before segments-after))))))
386 (define (schedule-extract-until! schedule time)
387 "Extract all segments until TIME from SCHEDULE, and pop old segments off"
388 (receive (segments-before segments-after)
389 (schedule-segments-split schedule time)
390 (set-schedule-segments! schedule segments-after)
393 (define (add-segments-contents-to-queue! segments queue)
396 (let ((seg-queue (time-segment-queue segment)))
397 (while (not (q-empty? seg-queue))
398 (enq! queue (deq! seg-queue)))))
403 ;;; Request to run stuff
404 ;;; ====================
406 (define-record-type <run-request>
407 (make-run-request proc when)
409 (proc run-request-proc)
410 (when run-request-when))
412 (define* (run-it proc #:optional when)
413 "Make a request to run PROC (possibly at WHEN)"
414 (make-run-request proc when))
416 (define-syntax-rule (wrap body ...)
417 "Wrap contents in a procedure"
421 (define-syntax-rule (wrap-apply body)
422 "Wrap possibly multi-value function in a procedure, applies all arguments"
427 ;; @@: Do we really want `body ...' here?
428 ;; what about just `body'?
429 (define-syntax-rule (run body ...)
430 "Run everything in BODY but wrap in a convenient procedure"
431 (make-run-request (wrap body ...) #f))
433 (define-syntax-rule (run-at body ... when)
435 (make-run-request (wrap body ...) when))
437 ;; @@: Is it okay to overload the term "delay" like this?
438 ;; Would `run-in' be better?
439 (define-syntax-rule (run-delay body ... delay-time)
440 "Run BODY at DELAY-TIME time from now"
441 (make-run-request (wrap body ...) (tdelta delay-time)))
444 ;; A request to set up a port with at least one of read, write, except
445 ;; handling processes
447 (define-record-type <port-request>
448 (make-port-request-intern port read write except)
450 (port port-request-port)
451 (read port-request-read)
452 (write port-request-write)
453 (except port-request-except))
455 (define* (make-port-request port #:key read write except)
456 (if (not (or read write except))
457 (throw 'no-port-handler-given "No port handler given.\n"))
458 (make-port-request-intern port read write except))
460 (define port-request make-port-request)
462 (define-record-type <port-remove-request>
463 (make-port-remove-request port)
465 (port port-remove-request-port))
467 (define port-remove-request make-port-remove-request)
471 ;;; Asynchronous escape to run things
472 ;;; =================================
474 (define-syntax-rule (8sync-abort-to-prompt async-request)
475 (abort-to-prompt (current-agenda-prompt)
478 ;; Async port request and run-request meta-requests
479 (define (make-async-request proc)
480 "Wrap PROC in an async-request
482 The purpose of this is to make sure that users don't accidentally
483 return the wrong thing via (8sync) and trip themselves up."
484 (cons '*async-request* proc))
486 (define (setup-async-request resume-kont async-request)
487 "Complete an async request for agenda-run-once's continuation handling"
489 (('*async-request* . async-setup-proc)
490 (async-setup-proc resume-kont))
491 ;; TODO: deliver more helpful errors depending on what the user
493 (_ (throw 'invalid-async-request
494 "Invalid request passed back via an (8sync) procedure."
497 (define-record-type <wrapped-exception>
498 (make-wrapped-exception key args stacks)
500 (key wrapped-exception-key)
501 (args wrapped-exception-args)
502 (stacks wrapped-exception-stacks))
504 (define-syntax-rule (propagate-%async-exceptions body)
505 (let ((body-result body))
506 (if (wrapped-exception? body-result)
507 (throw '8sync-caught-error
508 (wrapped-exception-key body-result)
509 (wrapped-exception-args body-result)
510 (wrapped-exception-stacks body-result))
515 "Run BODY asynchronously (8synchronously?) at a prompt, then return.
517 Possibly specify WHEN as the second argument."
521 (8sync-run-at body when))))
523 (define-syntax-rule (8sync-run body ...)
524 (8sync-run-at body ... #f))
526 (define-syntax-rule (8sync-run-at body ... when)
527 (propagate-%async-exceptions
528 (8sync-abort-to-prompt
529 ;; Send an asynchronous request to apply a continuation to the
530 ;; following function, then handle that as a request to the agenda
533 ;; We're making a run request
535 ;; Wrapping the following execution to run...
537 ;; Once we get the result from the inner part, we'll resume
538 ;; this continuation, but first
539 ;; @@: Is this running immediately, or queueing the result
540 ;; after evaluation for the next agenda tick? It looks
541 ;; like evaluating immediately. Is that what we want?
543 ;; Any unhandled errors are caught
544 (let ((exception-stack #f))
546 ;; Run the actual code the user requested
549 ;; If something bad happened and we didn't catch it,
550 ;; we'll wrap it up in such a way that the continuation
554 ((eq? key '8sync-caught-error)
556 ((orig-key orig-args orig-stacks)
557 (make-wrapped-exception
559 (cons exception-stack orig-stacks)))))
561 (make-wrapped-exception key args
562 (list exception-stack)))))
564 (set! exception-stack (make-stack #t 1 0)))))))
567 (define-syntax-rule (8sync-run-delay body ... delay-time)
568 (8sync-run-at body ... (tdelta delay-time)))
570 (define-syntax-rule (8sync-delay args ...)
571 (8sync-run-delay args ...))
573 (define-syntax-rule (8sync-port port port-request-args ...)
574 (8sync-abort-to-prompt
577 (list (make-port-request port port-request-args ...)
579 ;; What's with returning #f to kont?
580 ;; Otherwise we sometimes get errors like
581 ;; "Zero values returned to single-valued continuation""
582 (wrap (kont #f)) #f))))))
584 (define-syntax-rule (8sync-port-remove port)
585 (8sync-abort-to-prompt
588 (list (make-port-remove-request port)
590 ;; See comment in 8sync-port
591 (wrap (kont #f)) #f))))))
594 ;; TODO: Write (%run-immediately)
596 (define-syntax-rule (8sync-immediate body)
597 "Run body asynchronously but ignore its result...
598 forge ahead in our current function!"
599 (8sync-abort-to-prompt
602 (list (make-run-request
603 ;; See comment in 8sync-port
605 (make-run-request body #f))))))
607 (define-syntax-rule (catch-8sync exp (handler-key handler) ...)
608 (catch '8sync-caught-error
611 (lambda (_ orig-key orig-args orig-stacks)
613 ((or (eq? handler-key #t)
614 (eq? orig-key handler-key))
615 (apply handler orig-stacks orig-args)) ...
616 (else (raise '8sync-caught-error
617 orig-key orig-args orig-stacks))))))
621 ;;; Execution of agenda, and current agenda
622 ;;; =======================================
624 (define %current-agenda (make-parameter #f))
626 (define (update-agenda-from-select! agenda)
627 "Potentially (select) on ports specified in agenda, adding items to queue.
629 Also handles sleeping when all we have to do is wait on the schedule."
630 (define (hash-keys hash)
631 (hash-map->list (lambda (k v) k) hash))
632 (define (get-wait-time)
633 ;; TODO: we need to figure this out based on whether there's anything
634 ;; in the queue, and if not, how long till the next scheduled item
635 (let ((soonest-time (schedule-soonest-time (agenda-schedule agenda))))
637 ((not (q-empty? (agenda-queue agenda)))
639 (soonest-time ; ie, the agenda is non-empty
640 (let* ((current-time (agenda-time agenda)))
641 (if (time<= soonest-time current-time)
642 ;; Well there's something due so let's select
643 ;; (this avoids a (possible?) race condition chance)
645 (time-minus soonest-time current-time))))
649 ;; TODO: support usecond wait time too
650 (match (get-wait-time)
654 (select (hash-keys (agenda-read-port-map agenda))
655 (hash-keys (agenda-write-port-map agenda))
656 (hash-keys (agenda-except-port-map agenda))
658 (lambda (key . rest-args)
662 (_ (error "Unhandled error in select!" key rest-args))))))))
663 (define (get-procs-to-run)
664 (define (ports->procs ports port-map)
665 (lambda (initial-procs)
669 ((hash-ref port-map port) port))
674 ((read-ports write-ports except-ports)
675 ;; @@: Come on, we can do better than append ;P
676 ((compose (ports->procs
678 (agenda-read-port-map agenda))
681 (agenda-write-port-map agenda))
684 (agenda-except-port-map agenda)))
686 (define (update-agenda)
687 (let ((procs-to-run (get-procs-to-run))
688 (q (agenda-queue agenda)))
694 (define (ports-to-select?)
695 (define (has-items? selector)
697 ;; ... we could use hash-for-each and a continuation to jump
698 ;; out with a #t at first indication of an item
699 (not (= (hash-count (const #t)
702 (or (has-items? agenda-read-port-map)
703 (has-items? agenda-write-port-map)
704 (has-items? agenda-except-port-map)))
706 (if (or (ports-to-select?)
707 ;; select doubles as sleep...
708 (not (schedule-empty? (agenda-schedule agenda))))
712 (define (agenda-handle-port-request! agenda port-request)
713 "Update an agenda for a port-request"
714 (define (handle-selector request-selector port-map-selector)
715 (if (request-selector port-request)
716 ;; @@: Should we remove if #f?
717 (hash-set! (port-map-selector agenda)
718 (port-request-port port-request)
719 (request-selector port-request))))
720 (handle-selector port-request-read agenda-read-port-map)
721 (handle-selector port-request-write agenda-write-port-map)
722 (handle-selector port-request-except agenda-except-port-map))
725 (define (agenda-handle-port-remove-request! agenda port-remove-request)
726 "Update an agenda for a port-remove-request"
727 (let ((port (port-remove-request-port port-remove-request)))
728 (hash-remove! (agenda-read-port-map agenda) port)
729 (hash-remove! (agenda-write-port-map agenda) port)
730 (hash-remove! (agenda-except-port-map agenda) port)))
733 (define (stop-on-nothing-to-do agenda)
734 (and (q-empty? (agenda-queue agenda))
735 (schedule-empty? (agenda-schedule agenda))
736 (= 0 (hash-count (const #t) (agenda-read-port-map agenda)))
737 (= 0 (hash-count (const #t) (agenda-write-port-map agenda)))
738 (= 0 (hash-count (const #t) (agenda-except-port-map agenda)))))
741 (define* (start-agenda agenda
743 ;; @@: Should we make stop-on-nothing-to-do
744 ;; the default stop-condition?
745 (stop-condition stop-on-nothing-to-do)
746 (get-time gettimeofday)
747 (handle-ports update-agenda-from-select!))
748 ;; TODO: Document fields
749 "Start up the AGENDA"
750 (let loop ((agenda agenda))
752 ;; @@: Hm, maybe here would be a great place to handle
753 ;; select'ing on ports.
754 ;; We could compose over agenda-run-once and agenda-read-ports
755 (agenda-run-once agenda)))
756 (if (and stop-condition (stop-condition agenda))
759 ;; We have to update the time after ports handled, too
760 ;; because it may have changed after a select
763 ;; Adjust the agenda's time just in time
764 ;; We do this here rather than in agenda-run-once to make
765 ;; agenda-run-once's behavior fairly predictable
766 (set-field agenda (agenda-time) (get-time)))
767 (agenda-time) (get-time))))
768 ;; Update the agenda's current queue based on
769 ;; currently applicable time segments
770 (add-segments-contents-to-queue!
771 (schedule-extract-until! (agenda-schedule agenda) (agenda-time agenda))
772 (agenda-queue agenda))
776 (define (print-error-and-continue key . args)
777 "Frequently used as pre-unwind-handler for agenda"
779 ((eq? key '8sync-caught-error)
781 ((orig-key orig-args stacks)
782 (display "\n*** Caught async exception. ***\n")
783 (format (current-error-port)
784 "* Original key '~s and arguments: ~s *\n"
786 (display "* Caught stacks below (ending with original) *\n\n")
789 (display-backtrace s (current-error-port))
790 (newline (current-error-port)))
793 (format (current-error-port)
794 "\n*** Caught exception with key '~s and arguments: ~s ***\n"
796 (display-backtrace (make-stack #t 1 0)
797 (current-error-port))
798 (newline (current-error-port)))))
800 (define-syntax-rule (maybe-catch-all (catch-handler pre-unwind-handler)
802 (if (or catch-handler pre-unwind-handler)
807 (or catch-handler (lambda _ #f))
808 (or pre-unwind-handler (lambda _ #f)))
811 (define (agenda-run-once agenda)
812 "Run once through the agenda, and produce a new agenda
813 based on the results"
814 (define (call-proc proc)
816 (agenda-prompt-tag agenda)
818 (parameterize ((%current-agenda agenda))
820 ((agenda-catch-handler agenda)
821 (agenda-pre-unwind-handler agenda))
823 (lambda (kont async-request)
824 (setup-async-request kont async-request))))
826 (let ((queue (agenda-queue agenda))
827 (next-queue (make-q)))
828 (while (not (q-empty? queue))
829 (let* ((proc (q-pop! queue))
830 (proc-result (call-proc proc))
832 (lambda (run-request)
833 (define (schedule-at! time proc)
834 (schedule-add! (agenda-schedule agenda) time proc))
835 (let ((request-time (run-request-when run-request)))
837 ((? time-delta? time-delta)
838 (let ((time (time-delta+ (agenda-time agenda)
840 (schedule-at! time (run-request-proc run-request))))
842 (let ((time (cons sec 0)))
843 (schedule-at! time (run-request-proc run-request))))
844 (((? integer? sec) . (? integer? usec))
845 (schedule-at! request-time (run-request-proc run-request)))
847 (enq! next-queue (run-request-proc run-request))))))))
848 (define (handle-individual result)
849 ;; @@: Could maybe optimize by switching to an explicit cond...
851 ((? run-request? new-proc)
853 ((? port-request? port-request)
854 (agenda-handle-port-request! agenda port-request))
855 ((? port-remove-request? port-remove-request)
856 (agenda-handle-port-remove-request! agenda port-remove-request))
859 ;; @@: We might support delay-wrapped procedures here
862 (for-each handle-individual results))
863 (one-result (handle-individual one-result)))))
864 ;; TODO: Alternately, we could return the next-queue
865 ;; along with changes to be added to the schedule here?
866 ;; Return new agenda, with next queue set
867 (set-field agenda (agenda-queue) next-queue)))